The team from the University of Nottingham had previously shown that a high dose of creatine taken daily dramatically boosted glycogen stores in muscles. When the body's muscles run out of this carbohydrate energy, it is the equivalent of running out of fuel, and results in muscle fatigue.
"Glycogen is the fuel our muscles burn during intense exercise, and the amount our muscles can store can have a big impact on the length and quality of exercise," explained Professor Paul Greenhaff, lead author of the new study.
His team has now found that the dramatic response from supplementing with creatine, also found naturally in muscles, occurs within 24 hours after exercise, significantly boosting glycogen levels during recovery.
"Creatine itself is essential for sustaining the provision of energy during high intensity exercise," said professor Greenhaff, presenting the study at last week's Physiological Society conference in the UK.
"But when it is supplemented in the diet, it also has a major positive effect on glycogen storage. Basically, it leads to a dramatic increase in muscle glycogen stores in the initial 24 hours following exercise."
He added that while the compound has been associated with maximum power during sprint-type activity, the findings suggest that the supplement has further applications, such as in endurance sports.
To investigate when the response from creatine was occurring, the researchers studied the effects of the supplement on 14 men, with an average age of 26 years old. One group took 5g of creatine monohydrate, followed by 500ml of a carbohydrate solution, four times daily for six days. The placebo group replaced creatine with a glycine solution. Muscle samples were taken at baseline and on days one, three and six.
The subjects were required to exercise until exhaustion at the beginning of the study. They all followed a high carbohydrate diet during the study period.
"There was a clear statistical difference between the creatine and placebo groups. Now we need to test if performance indeed improved in these subjects," said Greenhaff.
He added that it is not clear if the same effects would be seen with a lower dose of creatine.The study also found that creatine had an effect on glycogen storage in muscles without significantly changing the levels of insulin in the blood, which could be important for people who are insulin intolerant.
The researchers now hope to investigate the processes at work. "As yet, it isn't clear exactly how it's happening, although it seems that the actual process of exercising is important in the effect creatine has," said Greenhaff. "If we can identify the mechanism involved, it opens up a lot of scope for independently changing muscle carbohydrate storage."
The study will be submitted for peer-reviewed publication.